Infrared-based metrology for detection of stress and defects around through silicon vias

ABSTRACT

An approach for IR-based metrology for detecting stress and/or defects around TSVs of semiconductor devices is provided. Specifically, in a typical embodiment, a beam of IR light will be emitted from an IR light source through the material around the TSV. Once the beam of IR light has passed through the material around the TSV, the beam will be analyzed using one or more algorithms to determine information about TSV stress and/or defects such as imbedded cracking, etc. In one embodiment, the beam of IR light may be split into a first portion and a second portion. The first portion will be passed through the material around the TSV while the second portion is routed around the TSV. After the first portion has passed through the material around the TSV, the two portions may then be recombined, and the resulting beam may be analyzed as indicated above.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending application Ser. No.13/769,494 filed Feb. 18, 2013.

BACKGROUND OF THE INVENTION

1. Technical Field

Embodiments of the present invention relate generally to infrared(IR)-based metrology. Specifically, embodiments of the present inventionrelate to the use of infrared (IR)-based metrology for the detection ofstress and effects around through silicon vias (TSVs).

2. Related Art

Thermal-mechanical reliability has become a big concern for theimplementation of through silicon vias (TSVs), which are a vital part of3D integration designs. Specifically, the process-induced stresses dueto CTE mismatch between silicon (Si) and copper (Cu) can causedetrimental effects on both the performance and reliability. Sucheffects include, among other, mobility degradation, Si cracking, devicede-bonding, and TSV pop-out.

As such, the measurement and handling of TSV stresses have become animportant part of device design and integration. Unfortunately, existingapproaches typically require cross-sectioning of the device such asduring use of processes such as electron microscopy. That is, microscopymay be limited by either sample surface topography or the requirement ofphysical damage to the sample being tested.

SUMMARY OF THE INVENTION

In general, aspects of the present invention relate to an approach forIR-based metrology for detecting stress and defects around/adjacent TSVsof semiconductor devices. Specifically, in a typical embodiment, a beamof IR light will be emitted from an IR light source through the materialaround a TSV. Once the beam of IR light has passed through the materialaround the TSV, the beam will be analyzed using one or more algorithmsto determine information about TSV defects such as imbedded cracking,etc. In one embodiment, the beam of IR light may be split into a firstportion and a second portion. The first portion will be passed throughmaterial around the TSV while the second portion is routed around theTSV. After the first portion has passed through the material around theTSV, the two portions may then be recombined, and the resulting beam maybe analyzed as indicated above.

A first aspect of the present invention provides a method for infrared(IR)-based metrology, comprising: passing a beam of IR light from an IRlight source through a material around a through silicon via (TSV) of asemiconductor device; and analyzing the beam of IR light after beingpassed through the material around a TSV to determine informationpertaining to stress or defects around the TSV.

A second aspect of the present invention provides a method for infrared(IR)-based metrology, comprising: emitting a beam of IR light using anIR light source; passing the beam of IR light through a material arounda through silicon via (TSV) of a semiconductor device along apredetermined path; and analyzing the beam after being passed throughthe material around a TSV to determine information pertaining to stressor defects around the TSV.

A third aspect of the present invention provides a method for infrared(IR)-based metrology, comprising: emitting a beam of IR light using anIR light source; splitting the beam of IR light into a first portion anda second portion; passing the first portion of the beam of IR lightthrough a material around a through silicon via (TSV) of a semiconductordevice; combining the first portion with the second portion after thepassing; and analyzing the beam after the combining to determineinformation pertaining to stress or defects around the TSV.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings in which:

FIG. 1 shows an example of a semiconductor device having a throughsilicon via (TSV) device experiencing defects.

FIG. 2 shows the use of IR-based metrology for analyzing TSV defectsaccording to an embodiment of the present invention.

FIG. 3 shows the use of IR-based metrology for analyzing TSV defectsaccording to another embodiment of the present invention.

The drawings are not necessarily to scale. The drawings are merelyrepresentations, not intended to portray specific parameters of theinvention. The drawings are intended to depict only typical embodimentsof the invention, and therefore should not be considered as limiting inscope. In the drawings, like numbering represents like elements.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments will now be described more fully herein withreference to the accompanying drawings, in which embodiments are shown.This disclosure may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough and complete and will fully convey the scope of this disclosureto those skilled in the art. In the description, details of well-knownfeatures and techniques may be omitted to avoid unnecessarily obscuringthe presented embodiments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of this disclosure.As used herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Furthermore, the use of the terms “a”, “an”, etc., do notdenote a limitation of quantity, but rather denote the presence of atleast one of the referenced items. The term “set” is intended to mean aquantity of at least one. It will be further understood that the terms“comprises” and/or “comprising”, or “includes” and/or “including”, whenused in this specification, specify the presence of stated features,regions, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Reference throughout this specification to “one embodiment,” “anembodiment,” “embodiments,” “exemplary embodiments,” or similar languagemeans that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the present invention. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” “in embodiments” and similar languagethroughout this specification may, but do not necessarily, all refer tothe same embodiment.

The terms “overlying” or “atop”, “positioned on” or “positioned atop”,“underlying”, “beneath” or “below” mean that a first element, such as afirst structure (e.g., a first layer) is present on a second element,such as a second structure (e.g. a second layer) wherein interveningelements, such as an interface structure (e.g. interface layer) may bepresent between the first element and the second element.

As indicated above, aspects of the present invention relate to anapproach for IR-based metrology for detecting stress and defectsaround/adjacent TSVs of semiconductor devices. Specifically, in atypical embodiment, a beam of IR light will be emitted from an IR lightsource through material around a TSV. Once the beam of IR light haspassed through the material around the TSV, the beam will be analyzedusing one or more algorithms to determine information about TSV defectssuch as imbedded cracking, etc. In one embodiment, the beam of IR lightmay be split into a first portion and a second portion. The firstportion will be passed through the material around the TSV while thesecond portion is routed around the TSV. After the first portion haspassed through the material around the TSV, the two portions may then berecombined, and the resulting beam may be analyzed as indicated above.

Referring to FIG. 1, an example of a semiconductor device 10 having TSV12 defects is shown. Specifically, as shown, TSV 12 has imbeddedcracking inside material 14 as well as a “keep-out” zone 16. Asindicated above such defects can greatly impact the design and/orintegration of such devices. In previous approaches, to completelyassess and address the defects, damage to the device was incurred due tonecessary cross-sectioning thereof. However, the current approachobviates this requirement by utilizing an IR light-based metrologyapproach.

Specifically, as will be shown and described in conjunction with FIGS.2-3, the present approach passes a beam of IR light through the materialaround a TSV, and then analyzes the resulting beam. Is general, thisapproach utilizes an IR light beam with photon energy smaller than Siband gap (1.12 eV) that becomes transparent and can thus can providein-depth information along the entire length of a TSV. In general, thefollowing principles and algorithms will be applied hereunder. One suchprinciple is that uniform “media” will generate well-defined periodicfringes. Such media can reveal various pieces of information about theTSV and/or its condition. According to the piezo-optic effect:Δε_(ij)(ω)=P _(ijkl)(ω)X _(kl)where X_(kl) is the stress tensor and P_(ijkl) is the piezo-optictensor. Thus, the distribution of stress or buried cracking defects leadto a perturbation of index of refraction along the beam path (as well asa stress dependent phase shift), which may be revealed by the followingalgorithm:

${\Delta\;{\phi\left( {x,y} \right)}} = {\int_{0}^{T}{\Delta\;{n\left( {x,y,z} \right)}\frac{2\pi}{\lambda}z{\mathbb{d}z}}}$where T is the total thickness of Si wafer. This results in distortionof fringes around the TSV, and the amount of distortion can be estimatedas: P˜10⁻⁹ Pa⁻¹, X˜100 Mpa, T˜100 m, so the phase shift is Δφ˜32 rad,which is a very significant effect.

Referring to FIG. 2, a direct imaging approach according to one aspectof the present invention is shown. As depicted, an IR light source 50emits a beam of IR light 52 (e.g., less than approximately 1.12 eV). Oneor more optics 54 may be used to direct beam 52 into TSV 58 ofsemiconductor device 56. Beam 52 will pass through the length of TSV 58.The resulting beam 60 will contain a perturbation of index of arefraction and other anomalies and may be received and analyzed bydetector 62 to determine information pertaining to stress or defectsaround TSV 58.

Referring to FIG. 3, an interferometry-based approach is shown. Asdepicted, a beam of IR light 72 is emitted from IR light source 70(e.g., less than approximately 1.12 eV). Beam 72 will be split by beamsplitter 73 into first portion 72A and second portion 72B. As furthershown, first portion 72A will be passed through TSV 76 of semiconductordevice 74 (e.g., via optic(s) 80A) while portion 72B is routed arounddevice 74. The resulting beam 78 will be recombined with portion 72B bybeam combiner 82 (e.g., via optic(s) 80B) to yield a recombined beam 84that will be analyzed by detector 86 similar to FIG. 2 to determineinformation about stress or defects in or around TSV 76. Using thisapproach may yield improved contrast and resolution and provide a basisfor comparison (i.e., between portion 72A passing through the materialaround the TSV 76 and portion 72B).

As shown and described, the IR-based approaches discussed herein canprovide a non-invasive, in-situ and high through-put detection of stressaround a TSV pattern. These approaches can also be used as a real timemonitor of stress during thermal cycling in order to prevent theformation of high stress and defects for process optimization. Moreover,the approaches can provide in-depth information regarding buried stressand/or defects around a TSV without cross sectioning the sample. Theinterferometry (phase sensitive) technique of FIG. 3 can provide muchbetter contrast, resolution and sensitivity.

In various embodiments, design tools can be provided and configured tocreate the data sets used to pattern the semiconductor layers asdescribed herein. For example, data sets can be created to generatephotomasks used during lithography operations to pattern the layers forstructures as described herein. Such design tools can include acollection of one or more modules and can also include hardware,software, or a combination thereof. Thus, for example, a tool can be acollection of one or more software modules, hardware modules,software/hardware modules, or any combination or permutation thereof. Asanother example, a tool can be a computing device or other appliance onwhich software runs or in which hardware is implemented. As used herein,a module might be implemented utilizing any form of hardware, software,or a combination thereof. For example, one or more processors,controllers, application-specific integrated circuits (ASIC),programmable logic arrays (PLA)s, logical components, software routines,or other mechanisms might be implemented to make up a module. Inimplementation, the various modules described herein might beimplemented as discrete modules or the functions and features describedcan be shared in part or in total among one or more modules. In otherwords, as would be apparent to one of ordinary skill in the art afterreading this description, the various features and functionalitydescribed herein may be implemented in any given application and can beimplemented in one or more separate or shared modules in variouscombinations and permutations. Even though various features or elementsof functionality may be individually described or claimed as separatemodules, one of ordinary skill in the art will understand that thesefeatures and functionality can be shared among one or more commonsoftware and hardware elements, and such description shall not requireor imply that separate hardware or software components are used toimplement such features or functionality.

While the invention has been particularly shown and described inconjunction with exemplary embodiments, it will be appreciated thatvariations and modifications will occur to those skilled in the art. Forexample, although the illustrative embodiments are described herein as aseries of acts or events, it will be appreciated that the presentinvention is not limited by the illustrated ordering of such acts orevents unless specifically stated. Some acts may occur in differentorders and/or concurrently with other acts or events apart from thoseillustrated and/or described herein, in accordance with the invention.In addition, not all illustrated steps may be required to implement amethodology in accordance with the present invention. Furthermore, themethods according to the present invention may be implemented inassociation with the formation and/or processing of structuresillustrated and described herein as well as in association with otherstructures not illustrated. Therefore, it is to be understood that theappended claims are intended to cover all such modifications and changesthat fall within the true spirit of the invention.

What is claimed is:
 1. A method for infrared (IR)-based metrology,comprising: passing a beam of IR light from an IR light source through amaterial around a through silicon via (TSV) of a semiconductor device;and analyzing the beam of IR light after being passed through thematerial around the TSV to determine information pertaining to stress ordefects around the TSV.
 2. The method of claim 1, the analyzingcomprising measuring a perturbation of a set of optical properties ofthe material around the TSV along a path of the beam of IR light.
 3. Themethod of claim 2, the measuring comprising applying the followingalgorithm:${{\Delta\;{\phi\left( {x,y} \right)}} = {\int_{0}^{T}{\Delta\;{n\left( {x,y,z} \right)}\frac{2\pi}{\lambda}z{\mathbb{d}z}}}},$wherein T is the total thickness of the semiconductor device, Δn(x,y,z)is the index of refraction perturbation due to stress at a location(x,y,z) in the semiconductor device, λ is the wavelength of the beam,and ΔΦ(x,y) is a phase perturbation on a plane (x,y) of thesemiconductor device.
 4. The method of claim 1, further comprising:emitting a beam of IR light from the IR source; and splitting the beaminto a first portion and a second portion, the passing comprisingpassing the first portion through the material around the TSV.
 5. Themethod of claim 4, further comprising combining the first portion andthe second portion after the first portion has passed through thematerial around the TSV.
 6. The method of claim 5, the analyzingcomprising analyzing the beam of IR light after the combining.
 7. Themethod of claim 1, the beam of IR light having a photon energy less thanapproximately 1.12 eV.
 8. A method for infrared (IR)-based metrology,comprising: emitting a beam of IR light using an IR light source;passing the beam of IR light through a material around a through siliconvia (TSV) of a semiconductor device along a predetermined path; andanalyzing the beam after being passed through the material around theTSV to determine information pertaining to stress or defects around theTSV.
 9. The method of claim 8, the analyzing comprising measuring aperturbation of an index of refraction along a path of the beam.
 10. Themethod of claim 9, the measuring comprising applying the followingalgorithm:${{\Delta\;{\phi\left( {x,y} \right)}} = {\int_{0}^{T}{\Delta\;{n\left( {x,y,z} \right)}\frac{2\pi}{\lambda}z{\mathbb{d}z}}}},$wherein T is the total thickness of the semiconductor device, Δn(x,y,z)is the index of refraction perturbation due to stress at a location(x,y,z) in the semiconductor device, λ is the wavelength of the beam,and ΔΦ(x,y) is a phase perturbation on a plane (x,y) of thesemiconductor device.
 11. The method of claim 8, further comprisingsplitting the beam of IR light into a first portion and a secondportion, the passing comprising passing the first portion through thematerial around the TSV.
 12. The method of claim 11, further comprisingcombining the first portion and the second portion after the firstportion has passed through the material around the TSV to yield arecombined beam of IR light.
 13. The method of claim 12, the analyzingcomprising analyzing the recombined beam of IR light.
 14. The method ofclaim 8, the beam of IR light having a photon energy less thanapproximately 1.12 eV.
 15. The method of claim 4, further comprisingrouting the second portion of the beam of IR light around the materialaround the TSV.
 16. The method of claim 1, the analyzing comprisingapplying an interferometry technique.
 17. The method of claim 1, themethod being performed in real-time.
 18. The method of claim 11, furthercomprising routing the second portion of the beam of IR light around thematerial around the TSV.
 19. The method of claim 8, the analyzingcomprising applying an interferometry technique.
 20. The method of claim8, the method being performed in real-time.